Electronic automatic meter reading (AMR) devices are used for flow metering in a pipeline. These devices typically use an electronic unit attached to a conventional magneto-mechanical or electronic flow meter, for example as disclosed in U.S. Pat. Nos. 4,940,976 and 6,611,769. Magneto-mechanical flow meters typically measure integrative water consumption by means of a mechanical gear. The accumulated liquid consumption is read by opto-electronic circuits, or by piezo-electric pick up of the gear rotation, which are usually packed in a dry section-register. In electronic meters, a magnetic sensor monitors the liquid meter rotor revolutions and generates an electrical signal indicative of the water flow. The sensor may be based, for example, on an inductive coil, a Hall effect sensor, or a magnetoresistive device. Some devices use optical pick-up systems to read the revolution of the magnetically driven revolutions of the rotor. The consumption and/or rate data is measured at various times and the data is transmitted to a central server typically via an RF link. AMR systems can also perform mass balance calculations by registering input and output flow at different locations in a pipe network. However, the AMR systems cannot detect leaks in pipes that are below their measurement threshold. AMR systems also cannot detect leaks that are less than 1% of the nominal flow in the distribution pipes nor locate the leak as the mass balance is done over a relatively large pipe network. Recently ultrasonic flow meters have been introduced that are based on sound velocity or Doppler phase shift measurements.
Several leak detection system and methods are known, such as vibration data loggers and correlators that measure pipe vibrations that are generated by the characteristic flow turbulence caused by a leak. This leakage detection is mostly based on vibration energy measurements and locating points where the vibration energy exceeds a particular threshold. A leak detection system based on vibration sensing is disclosed, for example, in U.S. Pat. No. 7,596,458.
Vibration data loggers include a vibration sensor such as a piezo element that is attached to a pipe element. The data logger is programmed to measure vibrations at certain times mostly at night when the flow is minimal. The signal processing of the logger calculates the vibrational energy at several locations of the pipe network, stores the calculated energies in a memory, and transmits the calculated energies to a processing station for leak detection using correlation analysis. Correlation analysis requires synchronization of the clocks of the sensors, and any drift in the clocks can adversely affect the accuracy of leak location.
The accuracy of the leak detection is increased with increasing number of sensors distributed over the pipeline network. A high density of the sensors provides high resolution and improved detection probability but increases the cost of the system. Nonetheless, existing noise loggers are very sensitive to artifacts due to noise generated by water consumption flow rather than leakage.